A path reuse method for specular surface reflection in Monte Carlo path tracing

Physically based image synthesis aims to render realistic images, which is widely used in many industries, e.g., computer-generated imagery (CGI) in the movie industry, 3D models preview in the architecture and the design industry, and of course, 3D scenes in the computer game industry. In the real world, the information of light is infinite; therefore, sampling is necessary for light contribution estimation. How to deal with global illumination effects plays an important role in whether the rendered image looks real or not. Many sampling methods reveal different features of the scene. Bidirectional path tracing, one of the Monte Carlo path tracing methods, is known for its rapid convergence. However, due to its innate limitation, bidirectional path tracing cannot handle some difficult cases. The most notorious one is specular-diffuse-specular (SDS) paths. In this paper, we introduce an alternative path reuse method based on bidirectional path tracing to deal with the SDS problem during the operation.